The annexed illustration shows a very common expedient. Suppose the waters of a river to be excessively turbid: a well may be dug in the bank at any convenient distance, and the water that collects in it will at least be much clearer than that of the river. Of course none of these modes will correct chemical impurity.
Hints on springs.
We have heard it said that even sea-water by filtration through a considerable mass of sand will lose much of its saltness and become drinkable, and that, by digging wells at some distance from the margin of the beach, it may be obtained with a very small amount of brackishness. We should like to hear a well-authenticated instance of this, in which there could be no doubt that the sea-water had been thus purified, and that the diggers had not in fact struck upon a stratum moistened by the inland drainage, and rendered more or less brackish by meeting with the sea-water.
We have known a remarkable instance of the discovery of a spring of fresh water in the immediate vicinity of the salt. In 1855, while attached to the North-Australian Expedition, we had great difficulty in supplying the sheep carried by our schooner, Tom Tough, with water. We made one trip up the Victoria River, with indiarubber bags—and this we purpose to notice more fully under its proper heading—and searched the country on either side the river in all directions. We found many little pools in shady hollows of rock, or of alluvial soil, marking the course the rivulets would take in the rainy season, and many of them decked with waterlilies. But these were too distant to be of service to us, and we again examined the country in our vicinity. In one cleft of rock we found a pint or two of water, and with a long twig and the broken shell of a gouty stem fruit we drew up enough to allay our thirst; but after traversing the arid ridges for hours we were returning unsuccessfully, when, passing at half-tide along the muddy margin of the river where a bold projecting headland forbade us any other path, Mr. Gregory noticed a little water collected in a hollow of the mud around a boulder. We thought at first it was only the drainage of the retiring tide, but on tasting it, we coincided in his opinion that it was not salt water. We set to work with our hands and cleared away the mud and brackish slime till, having reached a stratum too hard for our fingers’ ends, we rested, and soon had the satisfaction of seeing a small threadlike streamlet of clear water forcing its way through the muddy sediment. In a few minutes nearly half a pint of fresh water had collected, and, having satisfied ourselves of the value of our discovery, we returned to our schooner, and, putting a couple of puncheons in the long boat, waited till the turn of the next tide, and dropped down with the ebb to the headland. Our well was not yet uncovered, but we began to work as soon as the water fell below our knees, greatly to the astonishment of our Dutch sailor, who could hardly find terms strong enough to express it. “Allamagtig,” said he over and over again, “have I lived so long in this world that I must come to dig for fresh water underneath the salt!”
We made a fire on the uncovered boulder to give us light, at no small risk of injury from the splitting off of heated fragments; and, removing as many large stones as we could, cleared out a spring of perfectly pure fresh water, abundant enough to fill both our puncheons before the tide again rose high enough to cover it. Nor was this a transient phenomenon, for the next year, before we left the river, we again cleared out the “Gregory” well and filled all the casks of our vessel for her voyage. The sketch represents very nearly the locality in question; the high-water level is shown by the upper horizontal line, and the half-tide by the lower one, and that of the well is observable between them.
A makeshift filter can be made as follows: A small reed is inserted into a walnut shell, or any other receptacle of about the same size, pierced with small holes, and packed, not too tightly, with hemp, cotton, coir sponge, or other porous material; it is then placed in the shell of a cocoa-nut, an ostrich’s egg, or tin pannikin of any kind, and the interval between the two moderately packed with charcoal made either from wood or, still better, bones, with any fibrous material, and a mixture of sand or gravel. This is plunged beneath the water, and the tube being taken into the mouth, a little suction does all the rest. The shank or wing-bone of a crane, a stork, or albatross, may be used as a tube in the same manner.